Diesel fuel oil



United States Patent DIESEL FUEL on.

Maurice R. Barnsch, Richmond, Calif., and Robert Y.

Mixer, Kenmore, N. Y., a'ssignors to California Research Corporation,San Francisco, Calif;, a corporation of Delaware No Drawing. Originalapplication May 24, 1949, Serial No. 95,146, now Patent No. 2,655,440;dated October 13, 1953. Divided and this application June 8, 1953,Serial No. 360,373

6 Claims. (Cl. 44-57) This invention relates to an improved diesel fueloil, and more particularly to improved diesel fuel-oil compositionshaving high cetane numbers.

Diesel engines depend upon the heat developed by compressing a charge ofair to ignite the fuel injected into the engine cylinder after the airis compressed. A high compression ratio is necessary because .most knowndiesel 'fuels require a relatively high compression ratio in order toignite. A .factor of major importance in regard to the performance of adiesel fuel oil is the delay in ignition from the beginning of theinjection of the fuel to the beginning of. its combustion. This propertyis commonly termed the ignition-delay characteristic of the fuel and maybe expressed in terms of cetane numbers. If ignition delay is too long,the motor fuel will accumulate in the cylinder until it reaches ignitionconditions and then will burn rapidly, causing a sudden pressureincrease which may result in engine knocking. In addition, too long anignition delay may result in a smoky exhaust, a decrease in engineefiiciency, and possibly crankcase-oil dilution.

One of the more important dilficulties that arises through the use ofdiesel engines is the problem of starting the engine when it is cold. Itis quite common, when using many presently known diesel fuels, to employspecial starting procedures wherein various starting fuels, such asether, are employed. During the warm-up period of the diesel engines,considerable uneven ignition of the fuel may occur in the engine.

An object of the present invention is to provide a diesel fuel-oilcomposition having a high octane number that ignites readily andfunctions smoothly under operating conditions.

Another object of this invention is to provide a diesel fuel-oilcomposition that is readily adaptable for start ing cold diesel engines.

Still another object of this invention is to provide a high cetanenumber diesel 'fuel-oi1 composition whose base has a low cetane number.

A further object of this invention is to provide a diesel fuel-oilcomposition that may be used as a reference fuel for fuels having cetanenumbers in excess of 100.

In order to meet the increasing demand for diesel fuel oils having highcetane numbers, various cetane-improving materials have been added tothe petroleum fuel oil base. The use of cetane-improving materials hasalso permitted the employment of base fuels having relatively low cetanenumbers and has thereby increased, in many instances, the usefulness ofmiddle-of-the-barrel stock to the refiners. The cetane-improvingmaterials have been generally of an additive or blend type. Thecharacteristics and properties of these are described below.

We have discovered that when normally liquid oilsoluble aliphaticpolyethers, especially those having molecular weights below about 700with :a general formula:

2,763,537 Patented Sept. 18, 1956 wherein R and R are alkyl groups, X isa hydrocarbon group of the .alkylene type having at least two carbonatoms, and n is an integer, are blended with a diesel fuel oilcontaining a cetane-improving additive there is an unexpectedsynergistic cetane improvement.

The term cetane-improving additive as used herein and in the appendedclaims is a material that produces a relatively large cetane improvementwhen added in a small concentration to a diesel fuel oil. Theimprovement is independent of the cetane number of the additive and doesnot produce a corresponding cetane improvement when added in additionalincrementalamountss. Generally the amount of a cetane-improving additiveadded to a diesel fuel oil is in the range of about .001 per cent toabout 10 per cent.

Suitable additives which may be employed as the cetane-improvingadditive are: alkyl nitrate and nitrites; nitroso compounds; di-azocompounds; di-sulfides; and hydrocarbon peroxides such as di-alkylperoxides and alkyl hydroperoxides, including peroxides of the tertiaiytype and corresponding alicyclic per-oxides, and acyl peroxides. Thealkyl peroxides and hydroperoxides include the following specificcompounds: ethyl peroxide and hydroperoxide; isobutene peroxides andhydroperoxides; isopentene peroxides and hydroperoxides; Z-methylpentaneperoxides and hydroperoxides; 2-ethyl butene peroxide and hydroperoxide;Z-methylpentane peroxides and hydroperoxides; 3-methylpentane peroxideand hydroperoxide; 2.,3,-dimethyl butane peroxide and hydroperoxide; and2,4-dimethylbutane peroxide and hydroperoxide. Peroxides of thedi(tertiary alkyl) type include: di(tertiary butyl) peroxide;difitertiary amyl) peroxide; di(2-methyl, Z-pentyl) peroxides;di(3-methyl, 3-pentyl) peroxide; di(2-ethyl,2butyl) peroxide;di(lhalo,2-methyl,2-propyl) peroxide; di(1-halo,2-ethyl,2- propyl)peroxide; di(1 halo,2-methyl,2 butyl) peroxide;di(1-halo,3-methyl,3-butyl) peroxide; di(2-halo,3-methyl, Sabutyl)peroxide; di(l-phenyl,l-metl1yl,1-propyl) peroxide, and di(1phenyl,2-methyl,2-propyl) peroxide. Cyclic hydrocarbon peroxidesinclude: cyclopentyl hydroperoxide; methylcyclopentyl hydroperoxides;the isomeric dimethylcyclopentyl hydroperoxides; ethylcyclopentylperoxides; the isomeric diethylcyclopentyl hydroperoxides; the isomericmethylethylcyclopentyl hydroperoxides, cyclohexyl hydroperoxide,methylcyclohexyl hydroperoxides; the isomeric dimethylcyclohexylhydroperoxides; ethylcyclohexyl hydroperoxides; the isomericdiethylcyclohexyl hydropero-xides; l-4-methyl isopropylcyclohexylhyd-roperoxide; hydroperoxides of cyclopentane, cyclohep-tane, etc., andhigher moleculanweight substituted cycloparaflins. Asymmetrical dialkylperoxides may also be used.

Peroxides especially suitable for the composition of our invention arenon-benzenoid hydrocarbon peroxides which include the aliphatic andalicyclic peroxides. An example of these non-benzenoid peroxides isillustrated by the cetane-improving additive disclosed in Schultz et a1.Patent No. 2,317,968 and is prepared by partially oxidizing a petroleumdistillate relatively free from asphaltic and resinous materials andfrom large proportions of aromatic ring compounds, and of a highervolatility than kerosene with an oxygen-containing gas under liquidphaseconditions at a temperature of 275 to 310 F. for a sufficient length oftime to produce an oil having an oxygen factor (obtained by dissolvingan oil sample in 10 cc. of chloroform and 25 cc. of acetic acid and thenadding 2 cc. of saturated KI to the solution, agitating for 3 minutes,followed by titrating liberated iodine with NazSzOs and calculating theresults according to the equation: titer in ml. normality of thethiosulphate 1l20/vo1ume of sample in ml.) higher than 800, butinsuflicient to increase the neutralization number of the oil by morethan 20, then arresting said treatment before the oxygen factor of theproduced oil decreases to below 800 and then removing the acidicreaction products from the produced oil without reducing the oxygenfactor to below about 800.

Patent to Denison et al., No. 2,521,698, discloses another especiallydesirable non-benzenoid hydrocarbon peroxide for the composition of ourinvention which may be used as a cetane-improving material and that isprepared by subjecting a petroleum distillate having a boiling rangebetween 200 and 450 and relatively free from asphaltic and resinousmaterials and from large proportions of aromatic ring compounds to aliquidphase oxidation treatment with an oxygen-containing gas at atemperature within the range of 200 to 400 F. for a period of timesufficient to produce an oil having an oxygen factor higher than 250;contacting the resulting oxygenated oil with 0.1 to 0.75 pound of 5090per cent H2804 per gallon of oil at a temperature of 50 to 85 F. forless than 90 minutes, thereby producing a more stable and lesscorrosion-producing oil having a substantially lowered oxygen factor,treating this oil with controlled amounts of weak caustic solution toremove acidic ma terial, and concentrating the caustic-treated oil byfractional distillation to a temperature below 350 F. and a pressurebetween mm. of mercury and atmospheric to volatilize between 60 and 95per cent of said oxygenated oil to obtain a concentrate of relativelystable cetaneimproving oxygenated oil.

The term blending agent as used herein and in the appended claims is amaterial which produces a cetane improvement in diesel fuel oilscorresponding to the amount of blending agent added and the cetanenumber of the blending agent. The amount of blending agent generallyadded to diesel fuel oils is above about 5 per cent.

The aliphatic polyether blending agents especially suitable for thecomposition of this invention are normally liquid oil-soluble aliphaticpolyethers especially alkyl polyethers having a molecular weight belowabout 700 with a general formula:

wherein R and R are like or unlike alkyl groups, X is a hydrocarbongroup of the alkylene type having at least two carbon atoms, n is aninteger, and when n is more than one, X may be represented by like orunlike alkylene groups. The R and R radicals may be like or unlike andhave from 1 to 18 or more carbon atoms in each radical. The alkylenegroup X is a group having at least two carbon atoms and is preferablystraight chained. Examples of X wherein the nomenclature of alkyleneglycols is adopted, in which a CzH4 radical with two terminal bonds isconsidered to be an ethylene group, follow with the numbers indicatingsubstitution points: ethylene; 1,2 propylene; 1,3 propylene; 1,2butylene; 1,3 butylene; 1,4 butylene; 2,3 butylene; 1,2 pentylene; 1,3pentylene; 1,4 pentylene; 1,5 pentylene; 2,3 pentylene; 2,4 pentylene;1,2 hexylene; 1,3 hexylene; 1,4 hexylene; 1,5 hexylene; 1,6 hexylene;2,3 hexylene; 2,4 hexylene; 2,5 hexylene; 3,4 hexylene; 1,2 heptylene;1,3 heptylene; 1,4 heptylene; 1,5 heptylene; 1,6 heptylene; 1,7heptylene; 2,3 heptylene; 2,4 heptylene; 2,5 heptylene; 2,6 heptylene;3,4 heptylene; 3,5 heptylene; 1,2 octylene; 1,3 octylene; 1,4 octylene;1,5 octylene; 1,6 octylene; 1,7 octylene; 1,8 octylene; 2,3 octylene;2,4 octylene; 2,5 octylene; 2,6 octylene; 2,7 octylene; 3,4 octylene;3,5 octylene; 4,5 octylene; 3 ethyl, -2-4 hexylene; 1,3 dimethyl-Zethyl- 1,4 butylene, etc.

As explained above, X may be presented by unlike alkylene groups.Compounds having unlike X groups, for example, follow:

The blending agents also include alkylated polyalkylene oxides such asdiethyl poly 1,2-propylene oxide and diisopropyl poly ethylene oxide,etc.

The following examples illustrate cetane improvement obtained withcompositions of this invention.

The base fuel used in the examples below had the following inspection:

Source Straight-run California crude.

A. P. I. 37.6.

Viscosity at 100 F. 1.952 centistokes.

A. S. T. M. color 1-.

Lovibond color (through a 0.75.

500 series glass using 1" cell).

Flash point (Pensky-Martin) 152 F.

Carbon (Conradson 10% bot- 0.01.

toms).

Aniline point 138 F.

A. S. T. M. distillation:

Initial 358 F. 5% 399 F. 10% 404 F. 20% 416 F. 30% 428 F. 40% 440 F. 50%452 F. 60% 468 F. 70% 484 F. 80% 504 F. 532 F. 554 F. End point 594 F.

Cetane No. 43.

The method of determining the cetane numbers of fuels given in thetables below was A. S. T. M. Test No. D613-47T.

The symbol ACN is used to denote cetane number improvement over the basefuel. The cetane-improving additive used in Table I is the materialdisclosed in Patent No. 2,521,698 to Denison et a1. and described above.The numbers reported in the following tables are calculated from thecetane numbers obtained by the average of at least three different testson the same fuel.

Table I Percent AON pro- AON pro- Percent Diethylene duced by duced byAON Oetane- Glycol the Oetane- Diethylene Total AON Improving Di-EthylImproving Glycol Di- Oalcu- Observed Additive Ether Additive ethyl Etherlated (Alone) (Alone) 1 10 7 s 15 17 1 20 7 15 22 27 1 30 7 25 32 3s 21o 10 s 18 22 2 20 1o 15 25 30 2 30 10 25 35 42 10 10 23 8 31 35 10 2023 15 3s 4s 10 30 23 25 4s 57 From the foregoing table, it is apparentthat the ACN observed in all cases was substantially above the expectedimprovement which would be the summation of the cetane improvementobtained separately from the cetane-improving additive and from thediethylene glycol diethyl ether. Since cetane number can only beobtained up to 100, cetane numbers in excess of this are expressed interms of cetane (n-hexadecane) plus the number of cubic centimeters ofamyl nitrate per gallon of fuel required to match the fuel being tested.Cetane number above 100 is merely arelative term; anddeterminations ofsuch numbers generally do: not have a particularly significant meaning,and therefore. noreport has been included of a fuel having a cetanenumber above 100. However, as can be seen from the above table, a fuelhaving a cetane number above 100 is compounded" by merely increasing theamount of blending agent. For example, it is apparent from Table I- thata base fuel containing 40 per cent diethylene glycol diethyl ether and10 per cent of the cetane-improving additive would result in a fuel,having a cetane number substantially above 100.

Table II, below, is. a tabulation. of! results obtained when amylnitratewas used as the: cetane-improving, additive and when dimethoxytetraglycol was used: as; the blending agent.

Table II Percent AON pro- ACN pro- ACN Percent Dimedueed by duced byTotal ACN Am thoxy Amyl Dimethoxy Calcu- Observed Nitrate Tetra- NitrateTetraglycol lated glycol (Alone) (Alone) The results of Table II augmentthe results obtained in Table I and further show the synergisticimprovement of different additive plus different blending agents. Anoutstanding example of the improvement obtained by our invention is theabove-compounded diesel fuel oil containing one per cent amyl nitrate,20 per cent dimethoxy tetraglycol, wherein the difference between thecalculated improvement and the improvement obtained by actual testengine results was greater than 20 cetane numbers.

A further test was made to indicate the improvement obtainable with acomposition of our invention. In this test, a diesel fuel oil of thebase given above, was compounded with one per cent each of thecetane-improving additives of Tables I and II and additionally contained20 per cent of dimethoxy tetraglycol. The calculated cetane improvementwas 37, but the measured improvement from actual test engine resultsshowed an improvement of 50. Thus again this shows the cetaneimprovement obtainable with compositions of our invention.

To further illustrate the advantage obtainable by employing a dieselfuel oil composition of our invention, an addition of 10 per centdimethoxy tetraglycol was made to the base fuel and caused an increaseof 7 cetane numbers. To another sample of the base fuel was added 0.5per cent amyl nitrate and this addition caused an increase of 9 numbers.A one-to-one mixture of these two blends produced a fuel which has a 12number increase above the base stock which is considerably above theexpected number improvement. Normally when two fuels of different cetanenumber are blended in equal proportion, the resulting fuel has a cetanenumber equal to the average of its components.

In another example, equal portions of a fuel containing 10 per cent ofthe cetane-improving additive of Table I, which increased the rating ofthe base fuel 23 numbers, and a fuel containing 35 per cent ethyleneglycol dibutyl ether, which caused an increased rating of 20 numbers,were blended in a one-to-one ratio. The resultant fuel rated 32 numbersabove the base stock and again above the expected or calculated averageof 21.5 numbers.

When ethylene glycol dibutyl ether was added in equal proportions to apetroleum distillate having a cetane number of 43, the resulting fuelhad a cetane number of 78. Five per cent of tertiary butyl hydroperoxideincreased the cetane number of the petroleum distillate from 43 to 83. Aone-to-one mixture of these blended fuels resulted in an increase of 45cetane numbers over the base fuel or 7 cetane numbers above the expectedhaving a 43 cetane number, an increase of 12 cetane numbers resulted.However, when a one-to-oneblend of these two fuels was made a 17 cetanemember-over the- 43 resulted. This is 55 numbers above the expectedcalculated value.

The amount of cetane-improving additive in diesel fuel oil compositionsof our invention varies greatly and is generally preferred to be-withinthe range of 0501 to 10" per cent by weight. The, blending agent, alkylethers,

of our invention are usually employed in concentrationsgreater than 10per cent by weight. However, the amount of aliphatic polyethers may varyfrom about five per cent to about per cent of the total volume of thefuel of this invention with both the fuel-oil base and the polyethersbeing present in amounts exceeding five per cent by volume. Ordinarily,fuels suitable for commercial usage contain less than about 50 per centby volume of the polyethers. Fuels containing greater amounts of thepolyethers are suitable for high-cetane number test fuels. These alkylethers may be dior poly-ethers and have straight chain radicals orbranched chain radicals, with the former generally being preferred,although either, or mixtures thereof, may be employed in compositions ofour invention.

Because of the high cetane numbers available with compositions of ourinvention, the fuel compositions may be used as cold-engine startingfuels of diesel engines.

The fuel-oil base of the compounded diesel fuel oil of our invention maybe straight-run or cracked petroleum distillates or derived fromsynthetic processes or be mixtures thereof and boil in the range of fromabout 325 F. to about 750 F. The compound diesel fuel-oil composition issuitable as a fuel for engines of the diesel type, turbine type, and jettype.

This application is a division of our application, Serial No. 95,146,filed May 24, 1949, now Patent No. 2,655,- 440 granted Oct. 13, 1953,entitled Diesel Fuel Oil.

While various specific embodiments of the invention have beenillustrated and described, many modifications and adaptations may bemade without departing from this invention, and all such changes as areintended to be in cluded within the scope of the claims.

We claim:

1. An improved compression-ignition engine fuel consisting essentiallyof a major proportion of a mixture of a petroleum hydrocarbon fuel oilbase boiling in the range of about 325 F. to about 750 F. and anoil-soluble aliphatic polyether blending agent having a molecular weightbelow about 700 and the general formula:

wherein R and R are alkyl groups, X is a hydrocarbon group of thealkylene type having at least two carbon atoms and n is an integer, bothcomponents being present in amounts exceeding 5% of the total volume ofthe fuel and a minor proportion not exceeding 10% of the total volume ofthe fuel of amyl nitrate.

2. The composition of claim 1 wherein the oil-soluble aliphaticpolyether blending agent is dimethoxy tetraglycol.

3. The composition of claim 1 wherein the oil-soluble aliphaticpolyether blending agent is diethylene glycol dibutyl ether.

4. The composition of claim 1 wherein the oil-soluble aliphaticpolyether blending agent is diethylene glycol diethyl ether.

5. An improved compression-ignition engine fuel consisting essentiallyof a major proportion of a mixture of a petroleum hydrocarbon fuel oilbase boiling in the range of about 325 F. to about 750 F. and a normallyliquid oil-soluble aliphatic polyether blending agent having a molecularweight below about 700 and the general formula:

wherein R and R are alkyl groups containing from 1 to 18 carbon atoms, Xis an alkylene group having at least two carbon atoms and n is aninteger, both components being present in amounts exceeding 5% of thetotal volume of the fuel and a minor proportion not exceeding 10% of thetotal volume of the fuel of amyl nitrate.

6 A compounded diesel fuel oil consisting essentially of a majorproportion of a mixture of a straight-run California crude distillateboiling in the range of about 15 325 F. to about 750 F. and normallyliquid oil-soluwherein R and R are alkyl groups, X is an alkylene grouphaving at least two carbon atoms and n is an integer, both componentsbeing present in amounts exceeding 5% of the total volume of the fueland a minor proportion of at least 0.01% but not exceeding 10% by 0volume of amyl nitrate.

References Cited in the file of this patent UNITED STATES PATENTS

1. AN IMPROVED COMPRESSION-IGNITION ENGINE FUEL CONSISTING ESSENTIALLYOF A MAJOR PRPOPRTION OF A MIXTURE OF A PETROLEUM HYDROCARBON FUEL OILBASE BOILING IN THE RANGE OF ABOUT 325* F. TO ABOUT 750* F. AND ANOIL-SOLUBLE ALIPHATIC POLYETHER BLENDING AGENT HAVING A MOLECULAR WEIGHTBELOW ABOUT 700 AND THE GENERAL FORMULA: